Optical module

ABSTRACT

[Object] To suppress appearance of a ghost. 
     [Solving Means] The present optical module includes a sensor configured to pick up an image of an image pickup object, and a memory chip configured to store pixel data read out from the sensor and having the sensor joined thereto. The memory chip is connected to a substrate by a connection portion by flip-chip connection. The sensor can be connected by a wire to the memory chip, to which the sensor is joined. Further, the sensor can be joined to the memory chip in such a manner as to project toward an opening of the substrate. The present technology can be applied to a camera module.

CROSS REFERENCE TO RELATED APPLICATION

The present application is a continuation application of U.S. patentapplication Ser. No. 14/394,197, filed Oct. 14, 2014, which is aNational Stage of PCT/JP2013/002579, filed Apr. 16, 2013, and claims thebenefit of priority from prior Japanese Priority Patent Application JP2012-103133 filed in the Japan Patent Office on Apr. 27, 2012, theentire content of which is hereby incorporated by reference.

TECHNICAL FIELD

The present technique relates to an optical module, and particularly toan optical module which suppresses appearance of a ghost.

BACKGROUND ART

Recently, further downsizing of an optical module represented by acamera module to be incorporated in a portable telephone set, asmartphone or the like is attempted. FIG. 1 is a view showing aprinciple configuration of a cross section of such a conventionaloptical module 1 as just described.

In the optical module 1 shown in FIG. 1, a sensor 10 is configured froma logic section 11 and a light reception section 12. A circuit forprocessing pixel data outputted from the light reception section 12 isformed in the logic section 11. It is to be noted that a protrusionshown on the surface of the light reception section 12 represents apixel, and, while only three protrusions are shown in FIG. 1 forsimplified illustration, actually a great number of pixels are formed.

The sensor 10 is flip-chip (Flip Chip) connected at a periphery thereofto a substrate 14 by bumps 13. An opening 14A of the substrate 14 isclosed up with an infrared cut filter (IRCF) 15. Further, a retentionmember 16 for retaining a lens 17 is joined to the substrate 14.

By the configuration described above, light from an image pickup objectenters the light reception section 12 through the lens 17 and theinfrared ray cut filter 15. Pixel data generated by the pixels of thelight reception section 12 is processed by the circuit of the logicsection 11 and outputted to the outside.

Since the sensor 10 is flip-chip connected, reduction in size thereofcan be anticipated in comparison with an alternative case wherein thesensor 10 is wire-bonded.

CITATION LIST Patent Literature

[PTL1]

JP 2001-16486A

SUMMARY Technical Problem

Here, a ghost image is described. FIG. 2 illustrates a state ofreflection of light of the optical module 1 of FIG. 1. It is to be notedthat, as shown in FIG. 2, part of the light entering through the lens 17and the filter 15 (refer to FIG. 1) is reflected by an end face 14D ofthe substrate 14. Part of the reflected light advances toward the sensor10 and is received by the light reception section 12. In this manner,while only light passing through the lens 17 and the filter 15originally is to directly enter the light reception section 12, if thereflected light enters, then noise components enter and abnormality ofan image called ghost is likely to appear.

The present technology has been made in view of such a situation asdescribed above, and it is an object of the present technology tosuppress appearance of a ghost.

Solution to Problem

According to an aspect of the present technology, there is provided anoptical module including a sensor configured to pick up an image of animage pickup object, and a memory chip configured to store pixel dataread out from the sensor and having the sensor joined thereto, andwherein the chip sizes of the memory chip and the sensor are differentfrom each other and the sensor is placed at an upper portion of thememory chip.

The memory chip may be connected to a substrate through a connectionportion by flip-chip connection.

The sensor may be connected by a wire to the memory chip to which thesensor is joined.

The sensor may be joined to the memory chip so as to project toward anopening of the substrate from the memory chip.

The connection portion by the flip-chip connection may connect aperiphery of the memory chip to the substrate.

The wire may be connected at one end thereof to a periphery of a face ofthe sensor on the opening side and at the other end thereof to a regionof the memory chip between the connection portion by the flip-chipconnection and an end face of the sensor.

The sensor may be a stacked sensor.

A retention member which retains a lens for guiding light emergingtoward a filter so as to enter the sensor through the filter may bejoined to a face of the substrate opposing to the face of the memorychip to which the connection portion by the flip-chip connection isconnected.

The memory chip may be joined at a face thereof, on which the sensor isnot placed, to the substrate.

A retention member which retains a lens for guiding light emergingtoward a filter so as to enter the sensor through the filter may bejoined to the face of the substrate to which the memory chip is joined.

The memory chip may be connected, at the face thereof, to which thesensor is joined, to the substrate by a wire.

In the aspect of the present technology, an optical module including asensor configured to pick up an image of an image pickup object, and amemory chip configured to store pixel data read out from the sensor andhaving the sensor joined thereto, and the chip sizes of the memory chipand the sensor are different from each other and the sensor is placed atan upper portion of the memory chip.

Advantageous Effect of Invention

As described above, with the aspect of the present technology,appearance of a ghost can be suppressed.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a view showing a principle configuration of a cross section ofa conventional optical module 1.

FIG. 2 is a view illustrating a state of reflection of light of theoptical module 1.

FIG. 3 is a view showing a configuration of a cross section of anoptical module 101 of the present technique.

FIG. 4A and FIG. 4B are views illustrating an example of damage.

FIG. 5 is a block diagram showing a functional configuration of afabrication apparatus 501.

FIG. 6 is a flow chart illustrating a fabrication method for the opticalmodule 101.

FIG. 7A-FIG. 7E are views illustrating a fabrication process for theoptical module 101 of FIG. 3.

FIG. 8 is a view illustrating a state of reflection of light of theoptical module 101 of FIG. 3.

FIG. 9 is a view showing a configuration of a cross section of anotheroptical module 101 of the present technique.

FIG. 10 is a view illustrating a back focus.

FIG. 11 is a view illustrating a state of connection of a wire 120.

FIG. 12 is a view illustrating a state of reflection of light of theoptical module 101 of FIG. 9.

FIG. 13 is a view illustrating heat radiation.

FIG. 14A-FIG. 14E are views illustrating a fabrication process for theoptical module 101 of FIG. 9.

FIG. 15 is a view showing a configuration of a cross section of afurther optical module 101 of the present technique.

FIG. 16 is a view illustrating a state of reflection of light of theoptical module 101 of FIG. 15.

FIG. 17 is a flow chart illustrating a fabrication method for theoptical module 101 of FIG. 15.

FIG. 18A-FIG. 18D are views illustrating a fabrication process of theoptical module 101 of FIG. 15.

DESCRIPTION OF EMBODIMENTS

In the following, modes (hereinafter referred to as embodiments) forcarrying out the present technology are described. It is to be notedthat description is given in the following order.

1. First Embodiment (case wherein a non-stacked sensor is used)

[Structure of the Optical Module] [Configuration of the FabricationApparatus] [Fabrication Process]

2. Second Embodiment (case wherein a stacked sensor is used)

[Structure of the Optical Module] [Fabrication Process] [Modification][Fabrication Process] 3. [Other Configuration] 1. First Embodiment (CaseWherein a Non-Stacked Sensor is Used)

[Structure of the Optical Module] FIG. 3 is a view showing aconfiguration of a cross section of an optical module 101 of the presenttechnology. For example, in the optical module 101 which configures acamera module to be incorporated in a camera, a sensor 110 is configuredfrom a logic section 111 and a light reception section 112. A circuitfor processing pixel data outputted from the light reception section 112is formed in the logic section 111. The light reception section 112 isformed on the upper face side of a substantially central portion of thelogic section 111. In FIG. 3, protrusions shown in a semispherical shapeon an upper face of the light reception section 112 are portions whichconfigure pixels of red, green, blue and so forth, and include lensesfor converging light to corresponding light reception elements. In FIG.3, while only three protrusions are shown for simplified illustration,actually a great number of pixels are formed.

The sensor 110 is different in size from a memory chip 122. Inparticular, the sensor 110 is smaller in size than the memory chip 122and is directly joined in an overlapping relationship to an upper face122U substantially centrally of the memory chip 122 by a die bondmaterial 121. The memory chip 122 is a memory for storing pixel dataimaged by and outputted from the sensor 110 and is configured, forexample, from a DRAM (Dynamic Random Access Memory).

The memory chip 122 is flip-chip connected at a periphery thereof to aface 114B of the substrate 114 on the lower side in FIG. 3 through a pad118 by bumps 113, for example, of gold (Au) as a conductive material.The bumps 113 which are a flip-chip connection portion are sealed by anunderfill 119 applied for reinforcement.

An opening 114A for allowing light to enter the light reception section112 therethrough is formed substantially at the center of the substrate114. The sensor 110 is joined to the upper face 122U of the memory chip122 so as to project from the memory chip 122 into the opening 114A. Inparticular, since the size of the sensor 110 is smaller than that of thememory chip 122, a step is formed by the thickness of the sensor 110between the memory chip 122 and the sensor 110. A filter 115 is joinedto a face 114C of the substrate 114 on the upper side in FIG. 3 so as toclose up the opening 114A. The filter 115 prevents entering of infraredrays into the light reception section 112 and prevents dust fromdropping to the pixel face of the light reception section 112.

A lens unit 131 is configured from a retention member 116 and a lens 117retained by the retention member 116. The retention member 116 is joinedto the face 114C of the substrate 114 opposing to the face 114B.

The sensor 110 and the memory chip 122 are connected to each other bywires 120, for example, of gold as a conductive material. The wires 120are connected to a periphery of a face of the sensor 110 on the opening114A side and a region 122A of the memory chip 122 between the flip-chipconnected bumps 113 and an end face 110A of the sensor 110.

It is to be noted that an actuator for operating the lens 117 can beprovided in the retention member 116 such that also a so-calledautomatic focusing function is applied.

By the configuration described above, light from an image pickup objectenters the light reception section 112 through the lens 117 and thefilter 115. Pixel data generated by the light reception section 112 isprocessed by the circuit of the logic section 111 and outputted to theoutside.

In the present structure, since the flip-chip connection to the memorychip 122 is applied, even if supersonic vibration is utilized uponflip-chip connection, damage such as a crack does not appear at theconnection portion of the memory chip 122 to the substrate 114. Further,since the wires 120 which are stable in connection are connected to thesensor 110 and the memory chip 122, a robust structure design for aconnection structure is implemented and the connection quality isstabilized.

In particular, if the flip-chip connection is carried out for the logicsection 11 of the sensor 10 as shown in FIG. 1, then the sensor 10 issometimes damaged. This point is described with reference to FIG. 4A andFIG. 4B.

Several methods are available for the flip-chip connection of the sensor10. In a method in which solder or silver (Ag) paste is used for theconnection, a lens (lens (not shown) existing for each pixel of thelight reception section 12) on the sensor 10 is sometimes damaged byheat upon heating. Since also a method of pressure contacting gold (Au)and gold with each other requires heating, the lens is sometimes damagedsimilarly.

As a method for the flip-chip connection by which a low temperature isused for connection, a method is available wherein gold is joined inshort time by ultrasonic waves. However, this method has a problem thata portion connected by the bumps 13 of the logic section 11 is liable tobe damaged by the amplitude upon ultrasonic joining.

FIG. 4A and FIG. 4B are views showing an example of damage. In FIG. 4A,a portion connected by a bump 13 of the logic section 11 is shownsurrounded by a broken line. FIG. 4B shows a range surrounded by thebroken line in FIG. 4A in an enlarged scale. As shown in FIG. 4B, alow-relative dielectric constant film (Low-K film) 31 is formed at theportion of the logic section 11 connected by the bump 13, and aninterlayer film 32 is formed on the low-relative dielectric constantfilm 31. A process for joining the bump 13 by ultrasonic vibration iscarried out at the same time for all of the bumps 13 positioned on theperiphery of the sensor 10. As a result, arising from the ultrasonicvibration, damage such as a crack 33 sometimes appears on thelow-relative dielectric constant film 31 and the interlayer film 32.

In the optical module 101 of FIG. 3, the possibility is low that suchdamage as described above may appear.

It is to be noted that, as the sensor 110 of the optical module 101 ofFIG. 3, a sensor having a size equal to that of the sensor 10 of FIG. 1can be used. In this instance, in order to secure a region for formingthe bumps 113 therein, it is necessary to make the size (length in ahorizontal direction in FIG. 3) of the memory chip 122 greater than thatof the sensor 110. Therefore, even if a lens having a diameter equal tothat of the lens 17 of FIG. 1 is used as the lens 117, it is necessaryto make the outer diameter of the retention member 116 greater than thatof the retention member 16 of FIG. 1. Accordingly, the module size(outer diameter of the retention member 116) S11 of the optical module101 of FIG. 3 is greater than the module size (outer diameter of theretention member 16) S1 of the optical module 1 of FIG. 1.

Further, in the optical module 101 of FIG. 3, the position of the lightreception section 112 comes nearer to the lens 117 by a distance equalto the thickness of the sensor 110 in comparison with the optical module1 of FIG. 1. Accordingly, generally the length BF11 of a back focuswhich is a distance between the lens 117 retained by the retentionmember 116 and the light reception section 112 is shorter than thelength BF1 of the back focus which is the distance between the lens 17and the light reception section 12 of FIG. 1.

If the back focus is long, then the focal depth of the lens 117generally is great, and the fabrication dispersion is liable to beabsorbed with respect to the parallelism between the pixel face and thelens unit 131. Consequently, a fabrication process of a low cost can beimplemented. In particular, the lens unit 131 can be adhered to thesubstrate 114 while tilt correction of the lens unit 131 is not carriedout. In other words, if the length BF11 of the buck focus is setexcessively short, then this sometimes becomes disadvantageous.

In the case of an optical module which requires a back focus, the lengthof a gap G11 which is the length of the connection portion by the bumps113 of FIG. 3 (distance between the upper face 122U of the memory chip122 and the lower face 114B of the substrate 114) can be adjusted whennecessary. In particular, the length of the gap G11 can be set longerthan that of the gap G1 which is the length of the connection portion bythe bumps 13 of FIG. 1 (distance between the upper face 11U of the logicsection 11 and the lower face 14B of the substrate 14). Consequently,the length BF11 of the back focus can be set equal to or greater thanthe length BF1 of the back focus.

It is to be noted that the back focus is described in more detail withreference to FIG. 10 hereinafter described.

[Configuration of the Fabrication Apparatus]

Now, a fabrication apparatus 501 for the optical module 101 describedhereinabove is described. FIG. 5 is a block diagram showing a functionalconfiguration of the fabrication apparatus 501. As shown in FIG. 5, thefabrication apparatus 501 includes a preparation section 511, aconnection section 512, and a joining section 513.

The preparation section 511 prepares predetermined members. Theconnection section 512 carries out electric connection and so forth. Forexample, formation of bumps, flip-chip connection, wire bonding and soforth are carried out. The joining section 513 joins a sensor 110 andadheres a filter 115 and a lens unit 131.

[Fabrication Process]

Now, a fabrication method for the optical module 101 of FIG. 3 isdescribed. FIG. 6 is a flow chart illustrating a fabrication method forthe optical module 101, and FIG. 7A-FIG. 7E are views illustrating afabrication process of the optical module 101 of FIG. 3.

At step S1, the preparation section 511 prepares a memory chip 122 andso forth. Naturally, at this time, necessary members other than thememory chip 122 are prepared. For example, also a sensor 110, asubstrate 114, a filter 115, a lens unit 131 and so forth are prepared.At step S2, the connection section 512 forms bumps 113 on a periphery ofthe face 122U of the memory chip 122 on the upper side in FIG. 7A, asillustrated in FIG. 7A. For example, stud bumps are formed from a goldwire, and it is possible to form the connection gap G11 which is thedistance between the lower face 114B of the substrate 114 and the upperface 122U of the memory chip 122 at multiple stages as occasion demandsto adjust the same. Although, in the case of the present embodiment, thebump formation is carried out on the memory chip 122 after dicing, alsoit is possible to carry out the bump formation on a wafer for a memorybefore the dicing. In the case where the bumps are formed by plating,preferably they are formed on the wafer level.

Further, while, in the present fabrication method, the bumps 113 areformed on the memory chip 122 side, the bumps 113 may otherwise beformed on the substrate 114 side. In the case where the bumps 113 areformed at multiple stages, also it is possible to form the bumps 113 onboth of the memory chip 122 and the substrate 114 and flip-chip connectthe bumps 113.

At step S3, the connection section 512 carries out flip-chip connection.In particular, the memory chip 122 is connected to the lower face 114Bof the substrate 114 through the bumps 113 as shown in FIG. 7B. At thistime, ultrasonic vibration is utilized, and all bumps 113 on theperiphery of the memory chip 122 are connected at the same time. Sincethe low-relative dielectric constant film 31 or the interlayer film 32shown in FIG. 4A and FIG. 4B is not formed on the periphery of thememory chip 122, the possibility that damage such as a crack may appearis low. Further, to the bumps 113, an underfill 119 is applied forreinforcement to carry out sealing. Consequently, the memory chip 122 isflip-chip connected on the periphery thereof to the face 114B of thesubstrate 114 on the lower side in FIG. 7B through the pad 118 by thebumps 113.

Since the sensor 110 is mounted on the memory chip 122 later, at thistime, it is necessary to leave the opening 114A of the substrate 114open. If dust is placed on the pixel face of the light reception section112 of the sensor 110, then there is the possibility that the picturequality may be deteriorated. Therefore, it is necessary to select, asthe substrate 114, a substrate wherein dust does not appear from an endface of the opening 114A. Therefore, for the substrate 114, preferably aceramic substrate or an organic substrate whose opening 114A is coatedat an end face thereof to prevent appearance of dust.

At step S4, the joining section 513 joins the sensor 110. In particular,the sensor 110 is joined to the upper face 122U of the memory chip 122through a die bond material 121 as illustrated in FIG. 7C.

At step S5, the connection section 512 carries out wire bonding. Thisstate is illustrated in FIG. 7D. In particular, load is applied, forexample, by a capillary 301 (refer to FIG. 11 hereinafter described) toconnect the wires 120 between the sensor 110 and the memory chip 122.More particularly, the wires 120 are connected between a periphery of aface 110B of the sensor 110 on the opening 114A side and a region 122Aof the memory chip 122 between the flip-chip connected bumps 113 and theend face 110A of the sensor 110.

Although load and ultrasonic vibration are applied upon connection ofthe wires 120, this process is carried out for one by one of the wires120. As a result, the low-relative dielectric constant film 31 or theinterlayer film 32 (refer to FIG. 4A and FIG. 4B) of the logic section111 is scarcely damaged.

At step S6, the joining section 513 adheres the filter 115. Inparticular, the filter 115 is adhered to a face 114C of the substrate114 so as to close up the opening 114A as illustrated in FIG. 7E.

At step S7, the joining section 513 adheres the lens unit 131. Inparticular, a retention member 116 which retains a lens 117 is adheredat an end portion thereof to the face 114C of the substrate 114 asillustrated in FIG. 3.

It is to be noted that, in the fabrication flow described above, thesensor 110 is bonded by die bonding and wire bonding to the memory chip122 after the memory chip 122 is flip-chip connected to the substrate114. However, the memory chip 122 may be flip-chip connected to thesubstrate 114 after the sensor 110 is bonded to the memory chip 122 bydie bonding or wire bonding. In this instance, it is necessary toprepare such a collet as handles a wire for wire bonding so as not to bedeformed.

FIG. 8 illustrates a state of reflection of light of the optical module101 of FIG. 3. It is to be noted that, in FIG. 8, the width of an arrowmark which signifies light represents the amount of light. Since thelight amount is attenuated by reflection, the width of the arrow mark ofreflected light is smaller than the width of the incident light.

As shown in FIG. 8, also part of light entering through the lens 117 andthe filter 115 (refer to FIG. 3) is reflected by the end face 114D ofthe substrate 114, and part of the reflected light advances toward thesensor 110. However, since the sensor 110 projects in a direction towardthe opening 114A from the upper face 122U of the memory chip 122 and thelight reception section 212 is positioned higher than the upper face122U of the memory chip 122. Further, the light reception section 112 isspaced away from the end face 114D by a distance corresponding to theregion 122A.

As a result, the light amount of the reflected light entering the lightreception section 112 decreases in comparison with that in the case ofthe light reception section 12 of FIG. 2. In particular, in order toprevent light reflected in the optical module 101 from entering thelight reception section 112, the step provided by the thickness of thesensor 110 is utilized to cut part of the reflected light by the endface 110A of the sensor 110. Although part of the light reflected by thewires 120 enters the light reception section 112, the amount of thelight is small. Accordingly, the possibility that a ghost may appear islower in the case illustrated in FIG. 8 than in the case illustrated inFIG. 2.

2. Second Embodiment (Case Wherein a Stacked Sensor is Used) [Structureof the Optical Module]

Now, a second embodiment is described. FIG. 9 is a view showing aconfiguration of a cross section of another optical module 101 of thepresent technology. The configuration of the optical module 101 shown inFIG. 9 is basically same as that of the optical module 101 shown in FIG.3. In particular, while, in the optical module 101 of FIG. 3, the sensor110 is configured from a non-stacked sensor, the optical module 101 ofFIG. 9 is different from that in the case of FIG. 3 in that a sensor 210is configured from a stacked sensor. In the non-stacked sensor, thelight reception section 112 which receives light and outputscorresponding pixel data is formed on a plane same as that of the logicsection 111 which processes the pixel data outputted from the lightreception section 112, as shown in FIG. 3. In contrast, the stackedsensor has a structure wherein a light reception section 212 whichreceives light and outputs corresponding pixel data is stacked on alogic section 211 which processes the pixel data outputted from thelight reception section 212 as shown in FIG. 9.

Since the sensor 210 is a stacked sensor, the light reception section212 is formed on the logic section 211. As a result, the thickness ofthe sensor 210 is greater than that of the sensor 110. However, themagnitude (size) of the sensor 210 in a direction of the plane issmaller than that of the sensor 110 which is a non-stacked sensor.Therefore, in the case where a lens of a size equal to that of the lens17 of FIG. 1 is used as the lens 117 of FIG. 9, the diameter of theretention member 116 can be made equal to that of the retention member16. In other words, the module size S21 of the optical module 101 ofFIG. 9 can be made equal to or smaller than the module size S1 of theoptical module 1 of FIG. 1. Further, the module size S21 of the opticalmodule 101 of FIG. 9 can be made smaller than the sizes S11 and S13 ofthe optical modules 101 of FIG. 3 and an optical module 101 of FIG. 15hereinafter described.

Also in the present embodiment, the length of the gap G21 can beadjusted as occasion demands similarly as in the case of FIG. 3. FIG. 10is a view illustrating a back focus. As shown in FIG. 10, the gap G21which is a length of a connection portion by bumps 113 is the distancebetween the upper face 122U of the memory chip 122 and the lower face114B of the substrate 114. It is possible to make the length of the gapG21 greater than the length of the gap G1 of FIG. 1 and adjust thelength BF21 of the back focus to a length equal to or greater than thelength BF1 of the back focus of FIG. 1.

Further, also it is possible to adjust the length of the back focus notonly by making the gap G21 for flip chip connection longer but also bypolishing the sensor 210 to a thickness smaller than that of the sensor110 (or the sensor 10) together with or separately from such elongationof the gap G21.

With the structure of the sensor 10 of the optical module 1 of FIG. 1,the sensor 10 can be made thin only to a thickness of approximately 100to 200 μm. This is because, although the pixel face preferably is flat,if silicon which is a material of the sensor 10 is made thin, then awarp appears with the sensor 10, resulting in deterioration of thepicture quality in that the pixel face of the light reception section 12is positioned outside the focus of the lens 17 or the resolution dropsdue to the warp.

In the structure of the optical module 101 of the present technology,since the memory chip 122 which is made of silicon which assures theflatness exists below, the thickness of silicon on the sensor 210 sidecan be made small. For example, the thickness of the silicon can bereduced to approximately 30 μm. By joining the sensor 210 to the memorychip 122 in this manner, the thickness of the sensor 210 can be reducedby at least part of an amount by which the distance of the back focus isreduced by the thickness of the sensor 210. Comprehensively, the lengthBF21 of the back focus can be adjusted by adjusting at least one of thethickness of the sensor 210 and the length of the bumps 113 (length ofthe gap G21).

The gap G21 can be adjusted, for example, by adjusting the bumps 113among multiple stages or, in the case where the bumps 113 is formed byplating, by the thickness of the plating. Also it is possible to adjustthe gap G21 by increasing the pre-coat amount of the bumps 113 or silver(Ag) paste as a conductive material.

FIG. 11 is a view illustrating a state of connection of a wire 120. Asshown in FIG. 11, to a pad 118A in a region 122A of the upper face 122Uof a memory chip 122 between an end face 210A of the sensor 210 and anend face 114D of the substrate 114, the wire 120 is connected at one endthereof. The wire 120 is connected at the other end thereof to a pad118B of the sensor 210.

For the connection of the wire 120, a capillary 301 is used. Therefore,the distance L1 between the end face 210A of the sensor 210 and an endportion of the pad 118A on the left side in FIG. 11 and the distance L2from the end face 114D of the substrate 114 on the left side in FIG. 11to an end portion of the pad 118A on the right side in FIG. 11 aredefined by the size of the capillary 301.

On the upper side in FIG. 11, the substrate 14 of the optical module 1of FIG. 1 and the sensor 10 joined to the substrate 14 are shown forcomparison. The diameter of the opening 14A of the substrate 14 isrepresented by D11. By using a stacked sensor which is small in size andin which the capillary 301 can be used in the region 122A as the sensor210, it is possible to make the diameter D21 of the opening 114A of thesubstrate 114 equal to or smaller than the diameter D11. In other words,by forming the sensor 210 in the form of a stacked sensor in an SiP(System in Package) by wire bonding, the size of the optical module 101can be made equal to or smaller than the size of the optical module 1.

FIG. 12 represents a state of reflection of light of the optical module101 of FIG. 9. It is to be noted that, also in FIG. 12, the width of anarrow mark which signifies light represents a light amount. Since thelight amount decreases by the reflection, the width of an arrow mark ofthe reflected light is smaller than the width of the incident light.

As shown in FIG. 12, part of light entering through the lens 117 and thefilter 115 (refer to FIG. 9) is reflected by the end face 114D of thesubstrate 114, and part of the reflected light advances toward thesensor 210. However, the sensor 210 projects toward the opening 114Afrom the upper face 122U of the memory chip 122 (a step is formedbetween the sensor 210 and the memory chip 122), and the light receptionsection 212 is positioned higher than the upper face 122U of the memorychip 122. Further, the light reception section 212 is spaced away fromthe end face 114D by an amount of the region 122A.

As a result, the light amount of the reflected light entering the lightreception section 212 decreases in comparison with that of a case of thelight reception section 12 of FIG. 2. In other words, in order toprevent light reflected in the optical module 101 from being introducedto the light reception section 112, the step provided by the thicknessof the sensor 210 is utilized so that part of the reflected light is cutby the end face 210A of the sensor 210. Although part of the lightreflected by the wires 120 enters the light reception section 212, theamount of the light is very small. Accordingly, the possibility that aghost may appear is lower in the case illustrated in FIG. 12 than in thecase illustrated in FIG. 2.

FIG. 13 is a view illustrating heat radiation. As shown in FIG. 13, heatgenerated by the sensor 210 is transmitted to the memory chip 122 andthen radiated from the memory chip 122. Accordingly, a rise of thetemperature of the sensor 210 is suppressed, and degradation of pixeldata by heat is suppressed.

Further, since the memory chip 122 is directly joined immediately belowthe sensor 210 through the die bond material 121, the wiring distancebetween them, namely, the length of the wires 120, can be made short. Asa result, it is possible to accumulate pixel data from the sensor 210 ata high speed into the memory chip 122 thereby to allow a high speedimage process. Consequently, such an image process as global shutteringand increase of the dynamic range becomes possible. It is to be notedthat the optical module 101 of FIG. 9 is advantageous for high speedprocessing in comparison with an optical module 101 of FIG. 15hereinafter described. This is because, since the memory chip 122 andthe substrate 114 are not connected to each other by wires 120B as inthe case of FIG. 15, there is no influence of the parasitic capacitanceof the wires 120B.

Further, the height of the optical module 101 of FIG. 9 can be reducedby an amount corresponding to the thickness of the substrate 114 incomparison with the optical module 101 of FIG. 15 hereinafter describedsimilarly to the optical module 101 of FIG. 3.

It is to be noted that effects of the embodiment of FIG. 9 describedabove are exhibited similarly also with the embodiment of FIG. 3.[Fabrication Process]

A fabrication method of the optical module 101 of FIG. 9 is described.FIG. 14A-FIG. 14E are views illustrating a fabrication process of theoptical module 101 of FIG. 9. As apparent from comparison of FIG.14A-FIG. 14E with FIG. 7A-FIG. 7E, FIG. 14A-FIG. 14E are different fromFIG. 7A-FIG. 7E only in that the sensor 110 in the form of a non-stackedsensor of FIG. 7A-FIG. 7E is changed to the sensor 210 in the form of astacked sensor, and the other steps are similar to those in the case ofFIG. 7A-FIG. 7E. Accordingly, the fabrication apparatus and thefabrication method of the optical module 101 of FIG. 9 are basicallysimilar to those in the case shown in FIGS. 5 and 6.

At step S1, the preparation section 511 prepares a memory chip 122 andso forth. Naturally, at this time, necessary members other than thememory chip 122 are prepared. For example, also the sensor 210,substrate 114, filter 115, lens unit 131 and so forth are prepared. Atstep S2, the connection section 512 forms bumps 113 on a periphery ofthe face 122U of the memory chip 122 on the upper side in FIG. 14A, asillustrated in FIG. 14A. For example, stud bumps are formed from a goldwire, and it is possible to form the connection gap G21, which is adistance between the lower face 114B of the substrate 114 and the upperface 122U of the memory chip 122, at multiple stages as occasion demandsso as to allow adjustment. The formation of the bumps 113 may be carriedout on the memory chip 122 after dicing or may be carried out on a waferfor a memory before dicing. Where the bumps 113 are formed by plating,preferably they formed on the wafer level.

Further, while, in the present fabrication method, the bumps 113 areformed on the memory chip 122 side, the bumps 113 may otherwise beformed on the substrate 114 side. Where such bumps 113 are formed atmultiple stages, it is possible to form the bumps 113 on both of thememory chip 122 and the substrate 114 and flip-chip connect the bumps113.

At step S3, the connection section 512 carries out flip-chip connection.In particular, as shown in FIG. 14B, the memory chip 122 is connected tothe lower face 114B of the substrate 14 through the bumps 113. Then, anunderfill 119 is applied for reinforcement to the bumps 113 to seal thebumps 113. Consequently, the memory chip 122 is flip-chip connectedthrough the bumps 113 at a periphery thereof to the face 114B of thesubstrate 114 on the lower side in FIG. 14A through pads 118.

Since the sensor 210 is mounted on the memory chip 122 later, at thistime, it is necessary to keep the opening 114A of the substrate 114open. If dust is placed on the pixel face of the light reception section212 of the sensor 210, then there is the possibility that the picturequality may become poor. Therefore, it is necessary to select asubstrate wherein dust does not appear from an end face of the opening114A as the substrate 114. Therefore, preferably a ceramic substrate oran organic substrate wherein the end face of the opening 114A is coatedto prevent production of dust is used as the substrate 114.

At step S4, the joining section 513 joins the sensor 210. In particular,the sensor 210 is joined directly to the upper face 122U of the memorychip 122 through the die bond material 121 as illustrated in FIG. 14C.

At step S5, the connection section 512 carries out wire bonding. Thisstate is illustrated in FIG. 14D. In particular, load and ultrasonicvibration are applied by the capillary 301 to connect the wires 120 to aperiphery of the light reception section 212 of the sensor 210 and theregion 122A of the memory chip 122.

It is to be noted that, although load and ultrasonic vibration areapplied upon connection of the wires 120, this process is carried outfor one by one of wires 120. As a result, the memory chip 122 is seldomdamaged. However, there is the possibility that the characteristic ofthe memory chip 122 may be influenced by the load and the ultrasonicwave. Therefore, it is safer if the area of the memory chip 122 in whichwire bonding is to be carried out is determined as a region in whichformation of memory cells is inhibited while only a wiring line layer isformed similarly to the flip-chip connection portion as a precautionarymeasure.

At step S6, the joining section 513 adheres the filter 115. Inparticular, the filter 115 is adhered to the face 114C of the substrate114 so as to close up the opening 114A as illustrated in FIG. 14E.

At step S7, the joining section 513 adheres the lens unit 131. Inparticular, the retention member 116 which retains the lens 117 isadhered at an end portion thereof to the face 114C of the substrate 114as shown in FIG. 9.

It is to be noted that, in the fabrication flow described above, thesensor 210 is bonded to the memory chip 122 by die bonding and wirebonding after the memory chip 122 is flip-chip connected to thesubstrate 114. However, the memory chip 122 may be flip-chip connectedto the substrate 114 after the sensor 210 is bonded to the memory chip122 by die bonding and wire bonding. In this instance, it is necessaryto prepare such a collet for handling wires for wire bonding so as notto be deformed.

[Modification]

In the foregoing description, in order to prevent damage to the sensors110 and 210, the sensors 110 and 210 are adhered to the memory chip 122,and then the memory chip 122 is connected to the substrate 114 by thebumps 113. Also it is possible to connect the memory chip 122 to thesubstrate 114 by wires 120 in place of the bumps 113.

FIG. 15 is a view showing a configuration of a cross section of afurther optical module 101. In this optical module 101, a memory chip122 to which a sensor 210 is joined through a die bond material 121 isfurther connected directly to the substrate 114. Further, not only thesensor 210 and the memory chip 122 are connected to each other by wires120A, but also the memory chip 122 and the substrate 114 are connectedto each other by wires 120B.

Accordingly, as shown in FIGS. 3 and 9, the possibility of damage to thememory chip 122 can be reduced further in comparison with an alternativecase in which the memory chip 122 and the substrate 114 are connected toeach other by the bumps 113.

Since the optical module 101 of FIG. 15 does not utilize the bumps 113but uses only wire bonding, reduction in cost can be achieved incomparison with the optical modules 101 of FIGS. 3 and 9.

FIG. 16 is a view illustrating a state of reflection of light of theoptical module 101 of FIG. 15. As shown in FIG. 16, part of lightentering through the lens 117 and the filter 115 is reflected by an endface 116C of the retention member 116, and part of the reflected lightadvances toward the sensor 210. However, the sensor 210 projects in adirection toward the opening 116B from the upper face 122U of the memorychip 122 (a step is formed between the sensor 210 and the memory chip122), and the light reception section 212 is positioned higher than theupper face 122U of the memory chip 122. Further, the light receptionsection 212 is spaced away from the end face 116C by an amountcorresponding to the region 122A.

As a result, the amount of the reflected light entering the lightreception section 212 decreases in comparison with that in the case ofthe light reception section 12 of FIG. 2. In particular, in order toprevent light reflected in the optical module 101 from advancing to thelight reception section 212, the step by the thickness of the sensor 210is utilized to cut part of the reflected light by the end face 210A ofthe sensor 210. Although part of light reflected by the wires 120 entersthe light reception section 212, the amount of such light is small.Accordingly, the possibility that a ghost may appear is lower in thecase illustrated in FIG. 16 than in the case illustrated in FIG. 2. As aresult, restrictions to the design of the retention member 116 arereduced.

[Fabrication Process]

A fabrication method of the optical module 101 of FIG. 15 is describedwith reference to FIGS. 17 and 18A-18D. FIG. 17 is a flow chartillustrating a fabrication method of the optical module 101 of FIG. 15.FIG. 18A-FIG. 18D are views illustrating a fabrication process of theoptical module 101 of FIG. 15. It is to be noted that the fabricationapparatus for the optical module 101 of FIG. 15 is basically similar tothat in the case shown in FIG. 5.

At step S51, the preparation section 511 prepares a memory chip 122 andso forth. Naturally, at this time, necessary members other than thememory chip 122 are prepared. For example, also a sensor 210, asubstrate 114, a filter 115, a lens unit 131 and so forth are prepared.

At step S52, the joining section 513 joins the sensor 210. Inparticular, the sensor 210 is joined directly to the upper face 122U ofthe memory chip 122 through the die bond material 121 as shown in FIG.18A.

At step S53, the joining section 513 joins the memory chip 122. Inparticular, the memory chip 122 to which the sensor 210 is adhered isjoined directly to the upper face 114C of the substrate 114 through adie bond material 251.

At step S54, the connection section 512 carries out wire bonding. Inparticular, load and ultrasonic vibration are applied through thecapillary 301 so that the wires 120A are connected to a periphery of thelight reception section 212 of the sensor 210 and the upper face 122U ofthe memory chip 122 as shown in FIG. 18C. Further, the sensor 210 andthe substrate 114 are connected to each other by the wires 120B.

It is to be noted that, although load and ultrasonic vibration areapplied upon connection of the wires 120A and 1206, the process iscarried out for one by one of wires 120. As a result, the memory chip122 is scarcely damaged. While, particularly in the optical modules 101of FIGS. 3 and 9, the memory chip 122 and the substrate 114 areconnected to each other by the bumps 113, in the optical module 101 ofFIG. 15, also the memory chip 122 and the substrate 114 are connected toeach other by the wires 120. Accordingly, the optical module 101 of FIG.15 is less likely to be damaged in comparison with the optical modules101 of FIGS. 3 and 9. However, it is safer if formation of memory cellson the memory chip 122, in which wire bonding is applied, is inhibitedand the region 122A is used for formation only of a wiring line layer asa precautionary measure.

At step S55, the joining section 513 adheres the filter 115. Inparticular, the filter 115 is adhered to a face 116A of the retentionmember 116 of the lens unit 131 so as to close up the space 1166 of theretention member 116 through which light is to pass as shown in FIG.18D.

At step S56, the joining section 513 adheres the lens unit 131. Inparticular, the retention member 116 which retains the lens 117 isadhered at an end portion thereof to the face 114C of the substrate 114as shown in FIG. 15.

Also in the optical module 101 of FIG. 15, the length of the wires 120can be reduced in comparison with an alternative case wherein thesubstrate 14 in the optical module 1 of FIG. 1 is elongated and a memorychip is joined to some place of the extended substrate 14, andhigh-speed processing can be anticipated. Further, also in the opticalmodule 101 of FIG. 15, effects similar to those achieved by the opticalmodules 101 of FIGS. 3 and 9 can be achieved.

It is to be noted that the embodiment of the present technology is notlimited to the embodiment described hereinabove but various alterationscan be made without departing from the subject matter of the presenttechnology.

3. Other Configuration

The present technology can have such configurations as described below.

(1) An optical module, including:

a sensor configured to pick up an image of an image pickup object; anda memory chip configured to store pixel data read out from the sensorand having the sensor joined thereto, whereinthe chip sizes of the memory chip and the sensor are different from eachother and the sensor is placed at an upper portion of the memory chip.

(2) The optical module according to (1) above, wherein the memory chipis connected to a substrate through a connection portion by flip-chipconnection.

(3) The optical module according to (1) or (2) above, wherein the sensoris connected by a wire to the memory chip to which the sensor is joined.

(4) The optical module according to any of (1) to (3) above, wherein thesensor is joined to the memory chip so as to project toward an openingof the substrate from the memory chip.

(5) The optical module according to any of (2) to (4), wherein theconnection portion by the flip-chip connection connects a periphery ofthe memory chip to the substrate.

(6) The optical module according to any of (3) to (5) above, wherein thewire is connected at one end thereof to a periphery of a face of thesensor on the opening side and at the other end thereof to a region ofthe memory chip between the connection portion by the flip-chipconnection and an end face of the sensor.

(7) The optical module according to any of (1) to (6) above, wherein thesensor is a stacked sensor.

(8) The optical module according to any of (2) to (7) above, wherein aretention member which retains a lens for guiding light emerging towarda filter so as to enter the sensor through the filter is joined to aface of the substrate opposing to a face of the memory chip to which theconnection portion by the flip-chip connection is connected.

(9) The optical module according to (1) above, wherein the memory chipis joined, at the face thereof on which the sensor is not placed, to thesubstrate.

(10) The optical module according to (9) above, wherein a retentionmember which retains a lens for guiding light emerging toward a filterso as to enter the sensor through the filter is joined to the face ofthe substrate to which the memory chip is joined.

(11) The optical module according to (9) or (10) above, wherein thememory chip is connected, at a face thereof to which the sensor isjoined, to the substrate by a wire.

REFERENCE SIGNS LIST

-   -   101 Optical module, 110 Sensor, 111 Logic section, 112 Light        reception section, 113 Bump, 114 Substrate, 115 Filter, 116        Retention member, 117 Lens, 119 Underfill, 120 Wire, 121 Die        bond material, 122 Memory chip, 131 Lens unit

What is claimed is:
 1. An optical module, comprising: a sensorcomprising: a light reception section configured to generate pixel databased on light received from an image pickup object; and a logic sectionconfigured to process the generated pixel data; and a memory chipconfigured to store the processed pixel data, wherein the sensor isjoined to an upper face of the memory chip, and wherein the sensor issmaller in size than the memory chip.
 2. The optical module according toclaim 1, wherein the upper face of the memory chip faces the imagepickup object.
 3. The optical module according to claim 1, wherein thesensor is joined to the memory chip at a center of the upper face of thememory chip.
 4. The optical module according to claim 1, wherein thelight reception section is stacked on the logic section.
 5. The opticalmodule according to claim 1, further comprising a first substrateattached to a lower face of the memory chip, opposite to the upper face,via bumps or wires.
 6. The optical module according to claim 1, whereinthe sensor is joined to the memory chip via a plurality of wires.
 7. Theoptical module according to claim 6, wherein a plurality of capillariesare used to connect the plurality of wires from the sensor to the memorychip.
 8. The optical module according to claim 1, further comprising: alens configured to guide the light from the image pickup object towardsthe sensor, and a filter between the lens and the sensor, wherein thefilter is configured to filter infrared rays from the light guidedtowards the light reception section.
 9. The optical module according toclaim 8, further comprising a retention member configured to retain thelens over the sensor.
 10. The optical module according to claim 9,wherein the retention member further retains the filter over the sensor,and wherein the retention member is joined to a side of a firstsubstrate, the first substrate is joined to a lower face of the memorychip opposite to the upper face.
 11. The optical module according toclaim 9, wherein the retention member is joined to a second substrate,wherein a filter is joined to the second substrate, and wherein thesecond substrate is joined to a periphery of the upper face of thememory chip via a flip-chip connection.
 12. The optical module accordingto claim 1, wherein heat generated by the sensor is transferred to thememory chip, and wherein the transferred heat is radiated from thememory chip.
 13. The optical module according to claim 1, wherein thesensor is joined to the memory chip via a die bond material.
 14. Theoptical module according to claim 1, further comprising: a secondsubstrate attached to the upper face of the memory chip via a flip-chipconnection; and an underfill that encapsulates a bump of the flip-chipconnection, wherein an end face of the underfill is adjacent to an endface of the sensor, and an end face of the second substrate is adjacentto the end face of the sensor.
 15. The optical module according to claim14, wherein the end face of the underfill and the end face of the secondsubstrate are coplanar.
 16. The optical module according to claim 1,wherein the sensor is smaller in size than the memory chip in a firstdirection, the first direction is perpendicular to a second directionalong which the light enters the optical module.